Accuracy of tobramycin levels obtained from central venous access devices in patients with cystic fibrosis is technique dependent.

Peter Mogayzel, Emily Pierce, Joanne Mills, Annette McNeil, Karen Loehr, Rebecca Joplin, Steve McMahan, Kathryn Anne Carson

Research output: Contribution to journalArticle

Abstract

OBJECTIVE: Patients with cystic fibrosis (CF) frequently require prolonged aminoglycoside antibiotic therapy administered via central venous access devices (CVADs). Therefore, the effect of the volume of saline flush used prior to drawing blood on tobramycin levels obtained from CVADs was investigated to determine the potential for inappropriate drug dosing decisions. PATIENTS AND METHODS: This was a prospective study comparing tobramycin levels in blood samples obtained simultaneously from CVADs and from venipuncture. Two saline flushing protocols were tested. During Phase I, CVADs were flushed with 3 mL of normal saline. The saline flush volume was increased to 10 to 20 mL during Phase II. All patients had CF and ranged in age from 10 months to 20 years. RESULTS: Twenty-eight paired peak levels were collected from 19 patients during Phase I of the study, and 30 paired samples were obtained from 20 patients using the revised collection protocol during Phase II. The median (range) peak tobramycin level obtained from CVADs using the original flushing protocol was 13.1 (3.4 to 52.0) compared to 9.5 (3.1 to 46.4) microg/mL for those drawn peripherally. Use of CVAD-obtained levels would have caused inappropriate dosing changes in 43% of cases. Increasing the saline flush volume improved the accuracy of the tobramycin levels obtained from CVADs. Median peak tobramycin levels using the modified flushing protocol were 17.3 (3.6 to 47.0) and 19.0 (3.3 to 42.1) microg/mL obtained from a CVAD or venipuncture, respectively. The intraclass correlation coefficient for this protocol was 0.90 (lower 95% confidence limit = 0.80). Additionally, 87% of these CVAD-obtained levels provided accurate information for clinical decision making. CONCLUSIONS: Peak tobramycin levels drawn from CVADs flushed with a small flush volume are falsely elevated compared to those obtained by peripheral venipuncture. The use of a larger saline flush greatly improves the accuracy of these levels. Therefore, care should be taken to base clinical decisions on tobramycin levels obtained by peripheral venipuncture or following an appropriate large volume saline flush.

Original languageEnglish (US)
JournalPediatric nursing
Volume34
Issue number6
StatePublished - Nov 2008

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Tobramycin
Cystic Fibrosis
Equipment and Supplies
Phlebotomy
Aminoglycosides
Prospective Studies
Anti-Bacterial Agents

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Accuracy of tobramycin levels obtained from central venous access devices in patients with cystic fibrosis is technique dependent. / Mogayzel, Peter; Pierce, Emily; Mills, Joanne; McNeil, Annette; Loehr, Karen; Joplin, Rebecca; McMahan, Steve; Carson, Kathryn Anne.

In: Pediatric nursing, Vol. 34, No. 6, 11.2008.

Research output: Contribution to journalArticle

Mogayzel, Peter ; Pierce, Emily ; Mills, Joanne ; McNeil, Annette ; Loehr, Karen ; Joplin, Rebecca ; McMahan, Steve ; Carson, Kathryn Anne. / Accuracy of tobramycin levels obtained from central venous access devices in patients with cystic fibrosis is technique dependent. In: Pediatric nursing. 2008 ; Vol. 34, No. 6.
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title = "Accuracy of tobramycin levels obtained from central venous access devices in patients with cystic fibrosis is technique dependent.",
abstract = "OBJECTIVE: Patients with cystic fibrosis (CF) frequently require prolonged aminoglycoside antibiotic therapy administered via central venous access devices (CVADs). Therefore, the effect of the volume of saline flush used prior to drawing blood on tobramycin levels obtained from CVADs was investigated to determine the potential for inappropriate drug dosing decisions. PATIENTS AND METHODS: This was a prospective study comparing tobramycin levels in blood samples obtained simultaneously from CVADs and from venipuncture. Two saline flushing protocols were tested. During Phase I, CVADs were flushed with 3 mL of normal saline. The saline flush volume was increased to 10 to 20 mL during Phase II. All patients had CF and ranged in age from 10 months to 20 years. RESULTS: Twenty-eight paired peak levels were collected from 19 patients during Phase I of the study, and 30 paired samples were obtained from 20 patients using the revised collection protocol during Phase II. The median (range) peak tobramycin level obtained from CVADs using the original flushing protocol was 13.1 (3.4 to 52.0) compared to 9.5 (3.1 to 46.4) microg/mL for those drawn peripherally. Use of CVAD-obtained levels would have caused inappropriate dosing changes in 43{\%} of cases. Increasing the saline flush volume improved the accuracy of the tobramycin levels obtained from CVADs. Median peak tobramycin levels using the modified flushing protocol were 17.3 (3.6 to 47.0) and 19.0 (3.3 to 42.1) microg/mL obtained from a CVAD or venipuncture, respectively. The intraclass correlation coefficient for this protocol was 0.90 (lower 95{\%} confidence limit = 0.80). Additionally, 87{\%} of these CVAD-obtained levels provided accurate information for clinical decision making. CONCLUSIONS: Peak tobramycin levels drawn from CVADs flushed with a small flush volume are falsely elevated compared to those obtained by peripheral venipuncture. The use of a larger saline flush greatly improves the accuracy of these levels. Therefore, care should be taken to base clinical decisions on tobramycin levels obtained by peripheral venipuncture or following an appropriate large volume saline flush.",
author = "Peter Mogayzel and Emily Pierce and Joanne Mills and Annette McNeil and Karen Loehr and Rebecca Joplin and Steve McMahan and Carson, {Kathryn Anne}",
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T1 - Accuracy of tobramycin levels obtained from central venous access devices in patients with cystic fibrosis is technique dependent.

AU - Mogayzel, Peter

AU - Pierce, Emily

AU - Mills, Joanne

AU - McNeil, Annette

AU - Loehr, Karen

AU - Joplin, Rebecca

AU - McMahan, Steve

AU - Carson, Kathryn Anne

PY - 2008/11

Y1 - 2008/11

N2 - OBJECTIVE: Patients with cystic fibrosis (CF) frequently require prolonged aminoglycoside antibiotic therapy administered via central venous access devices (CVADs). Therefore, the effect of the volume of saline flush used prior to drawing blood on tobramycin levels obtained from CVADs was investigated to determine the potential for inappropriate drug dosing decisions. PATIENTS AND METHODS: This was a prospective study comparing tobramycin levels in blood samples obtained simultaneously from CVADs and from venipuncture. Two saline flushing protocols were tested. During Phase I, CVADs were flushed with 3 mL of normal saline. The saline flush volume was increased to 10 to 20 mL during Phase II. All patients had CF and ranged in age from 10 months to 20 years. RESULTS: Twenty-eight paired peak levels were collected from 19 patients during Phase I of the study, and 30 paired samples were obtained from 20 patients using the revised collection protocol during Phase II. The median (range) peak tobramycin level obtained from CVADs using the original flushing protocol was 13.1 (3.4 to 52.0) compared to 9.5 (3.1 to 46.4) microg/mL for those drawn peripherally. Use of CVAD-obtained levels would have caused inappropriate dosing changes in 43% of cases. Increasing the saline flush volume improved the accuracy of the tobramycin levels obtained from CVADs. Median peak tobramycin levels using the modified flushing protocol were 17.3 (3.6 to 47.0) and 19.0 (3.3 to 42.1) microg/mL obtained from a CVAD or venipuncture, respectively. The intraclass correlation coefficient for this protocol was 0.90 (lower 95% confidence limit = 0.80). Additionally, 87% of these CVAD-obtained levels provided accurate information for clinical decision making. CONCLUSIONS: Peak tobramycin levels drawn from CVADs flushed with a small flush volume are falsely elevated compared to those obtained by peripheral venipuncture. The use of a larger saline flush greatly improves the accuracy of these levels. Therefore, care should be taken to base clinical decisions on tobramycin levels obtained by peripheral venipuncture or following an appropriate large volume saline flush.

AB - OBJECTIVE: Patients with cystic fibrosis (CF) frequently require prolonged aminoglycoside antibiotic therapy administered via central venous access devices (CVADs). Therefore, the effect of the volume of saline flush used prior to drawing blood on tobramycin levels obtained from CVADs was investigated to determine the potential for inappropriate drug dosing decisions. PATIENTS AND METHODS: This was a prospective study comparing tobramycin levels in blood samples obtained simultaneously from CVADs and from venipuncture. Two saline flushing protocols were tested. During Phase I, CVADs were flushed with 3 mL of normal saline. The saline flush volume was increased to 10 to 20 mL during Phase II. All patients had CF and ranged in age from 10 months to 20 years. RESULTS: Twenty-eight paired peak levels were collected from 19 patients during Phase I of the study, and 30 paired samples were obtained from 20 patients using the revised collection protocol during Phase II. The median (range) peak tobramycin level obtained from CVADs using the original flushing protocol was 13.1 (3.4 to 52.0) compared to 9.5 (3.1 to 46.4) microg/mL for those drawn peripherally. Use of CVAD-obtained levels would have caused inappropriate dosing changes in 43% of cases. Increasing the saline flush volume improved the accuracy of the tobramycin levels obtained from CVADs. Median peak tobramycin levels using the modified flushing protocol were 17.3 (3.6 to 47.0) and 19.0 (3.3 to 42.1) microg/mL obtained from a CVAD or venipuncture, respectively. The intraclass correlation coefficient for this protocol was 0.90 (lower 95% confidence limit = 0.80). Additionally, 87% of these CVAD-obtained levels provided accurate information for clinical decision making. CONCLUSIONS: Peak tobramycin levels drawn from CVADs flushed with a small flush volume are falsely elevated compared to those obtained by peripheral venipuncture. The use of a larger saline flush greatly improves the accuracy of these levels. Therefore, care should be taken to base clinical decisions on tobramycin levels obtained by peripheral venipuncture or following an appropriate large volume saline flush.

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